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Lectures > On Set Noise Investigation

On Set Noise Investigation

by The Association of Motion Picture Sound

Introduction

In response to complaints from Production Sound members regarding on set noise problems that inhibit the recording of usable sound and cause undue stress on sound crews, AMPS called a meeting of members to discuss the matter and offer solutions. Resulting from this meeting, a cross-section of members was asked to reply to a survey seeking their opinions and experiences under the following categories:

The following is a summary of the remarkably similar comments and opinions expressed.

1- Lighting Equipment

The main source for on set noise was identified as the Lighting Equipment, in particular HMI chokes and heads, with the brand names Desisti and Arrisun mentioned more than once.

The noise caused by use of cooling fans in electronic ballast chokes makes the recording of usable sound almost impossible. The lack of clear instruction to the lighting crew when to switch the ballasts from noisy “flicker free” to silent synchronous running mode is a problem.

“Flicker Free” is only necessary to avoid any stroboscopic effects when the camera is running at a non-standard frame rate for slow or fast motion.

With a stable 50 Hz AC generator and crystal controlled camera motor, there is no “Flicker” problem if at 24 FPS the camera shutter is set to 172.8º, and at 25 FPS at the same mains frequency the shutter is set to 180º.

Buzzing dimmer boards were also singled out as a source of noise. Not only does this equipment cause acoustic problems, but now we are faced with horrendous electromagnetic interference from cables and heads, affecting microphone cables and even the microphones themselves.

Star Quad microphone cables can help but are not a complete cure. There are new EEC Regulations in place governing the emission of electro-magnetic interference from any equipment manufactured since January 1996 so perhaps manufacturers could be persuaded to look into the problem with this in mind. Although modern generators are quite well blimped, they still need careful placing and the Sound Mixer should be consulted where possible.

We need to do something about the lighting equipment problem collectively instead of leaving it all to the man on the spot. A letter from AMPS will be composed and sent to all the main Lighting Companies and Manufacturers to voice our concern over the trend to noisy equipment.

2- Camera Equipment

It appears that we have, on the whole, won the camera noise battle, our continuous 'whinging' has worked! Even Arriflex has decided to enter the Sound Movie Era with their latest generation of cameras although there are still enough old 35BL cameras around to cause problems on lower budget movies. Film magazines on Panaflex cameras were mentioned as a cause of problems but co-operation with the Sound Department is now customary and a magazine can be swiftly blimped or replaced. However, it is still a common practice to bring in the unblimped second camera if it is “only effects”. These effects cost money and time to replace and are then often not as good as the original, in spite of the best efforts of the Sound Editor. Some education is necessary in this area.

Another source of noise identified was video recorders, they need blimping or placing off set which is difficult when it is part of the camera on a video shoot!

3- Base Camp and Crew Discipline

Crew generated noises were common complaints and a finger pointed at the responsibility of the First Assistant Director and his assistants in maintaining crew discipline. The advent of mobile phones and proliferation of walkie talkies cause many problems, spoiling good takes and wasting expensive film.

The studio red light discipline needs to be reinforced and all crew members reminded of their responsibility to remain silent during shooting.

The rule of soft soled footwear for crew members that used to be applied to studio work is now largely forgotten and needs to be re-introduced.

A red light and Bell system should be employed on Base Camp where possible to inform everyone that the camera is turning.

A single generator for the service vehicles provides a more controllable source of noise than endless Honda noise boxes. There is a production financial consideration with the single generator approach as it may be necessary to employ an electrician to supervise the rig, but this must be weighed up against the cost of the shooting time wasted turning off all the individual generators or subsequent post-production work on the sound.

4- Studio and Location Choice

The main point raised under location and studio choice was that the Sound Mixer should be present at all location recces and production meetings to advise the production on the suitability for sound. This means employing the Sound Mixer a few extra days before production, but again this cost must be weighed against the cost of post-production, the loss of performances from the artists, and the subsequent earache from the sound department when they complain! The Sound Mixer can spot sound problems, such as air conditioning noise, so often missed during a recce, and arrange to have control of it prior to shooting. Using poorly built 'studios' and warehouses in which to build sets causes many sound problems, particularly when rain or hail hits the non-insulated roof, often overlooked by production in their efforts to save money.

Studio maintenance was also criticised, in particular badly fitting doors and locks that do not work. This point should be raised with the various studio managements by AMPS.

5- Costumes and Sets

On the question of Costumes and Sets, it was suggested that if the Sound Mixer was employed early enough in the pre-production period, some of the obvious problems could be avoided using his experience and advice, in liaison with the relevant departments.

A careful choice of costume materials and adding soft soles to shoes can produce fewer problems for sound post-production. Wardrobe and Production staff need to be educated on the necessity of this practice. Noisy props need the attention of the Sound Department since sometimes they end up with a bigger part than the stars!.

A supply of Tesamol foam rubber tape is an essential Sound Department requirement to deaden shoes and props. Built set floors are a particular problem, particularly when built on rostrums. Some substantial stiffening should be added to compensate for the weight of the camera and crew to prevent any creaking.

Floor boards should be laid on a firm base so that they cannot move and spaced slightly apart to avoid any rubbing, and for the same reason, “tongue and groove” flooring should be avoided.

6- Other sources of noise

Tracking noise was mentioned on several surveys and the lack of experience in building and operating quiet tracking by the Grips Department.

There were several suggestions on using carpet or felt under the track to reduce feet noises and creaks.

Liberal amounts of WD40 sprayed on the wheels and rails, or talcum powder on the boards helps to reduce squeaks from dolly wheels. Also Special Effects smoke machines and gas fires were targeted as sources of unnecessary noise and it is often possible to effectively silence both effects.

If the Sound Mixer can have time before production to build up a good rapport with the other departments, and the “team spirit” emphasised, this is usually the best way to tackle these problems.

Constantly changing background noises between shots cause serious cutting and dubbing problems. The general misconception that it can be “fixed in the dub” was criticised by some of our post-production members who have to split up dialogue tracks line by line in order to filter varying noises during the dub, adding considerably to the workload while post-production schedules are getting shorter.

Summary

The ultimate authority for any noise generated on the set must rest with the Sound Mixer. He is professionally engaged to record usable sound and thus the production and Director should back him up. After all, it is their time and money that they are wasting by not listening and very few sound members do the job for fun!.


© 2006 The Association of Motion Picture Sound